Flowers and Fruits
Article #335 June 2022
By Bill Cook
All trees have flowers and fruits, although this may come as a surprise to some. The diversity by which trees embrace their reproduction imperative is amazing.
There are 75 to 80 species of trees across the Lake States. This number depends upon what might be considered a “tree” but let’s not quibble about that. Nearly all of them flower in the spring and most produce fruit in the same year. There are exceptions to this generality, but that’s part of the fun.
Taxonomists first divide tree species into softwoods (Gymnosperms) and hardwoods (Angiosperms). Botanically, the softwoods don’t have flowers, but they do have all the necessary hardware to produce fruits, usually in the form of a cone. So, let’s just say softwood flowers are different than hardwood flowers.
With softwoods, or conifers, pollen carries the sperm and the female cone contains the ovules. In the spring, clouds of pollen can sometimes be seen coating nearly every surface, much to the chagrin of people who are allergic to these pollens, or despise dusty cars. The male cones don’t last for long and the fertilized female cones ripen into the familiar woody or papery cones. Cones are the fruits of conifer trees with seeds on the inside.
When ripe, the cone scales open and the seeds flutter to the ground on the breeze. Each seed has a little wing that helps carry them away from the parent tree.
There are exceptions.
White-cedar cones don’t look much like cones, but they have papery scales, light green at first, then tan colored when mature. Redcedars and yews have berry-like fruits.
One cone that you’ll seldom see is from the balsam fir. These sticky, gooey cones develop at the top of the tree and disintegrate there, scale by scale, while releasing the seeds.
The majority of trees and tall shrubs are hardwoods, or broad-leafed trees (Angiosperms). All of these species have true flowers with the botanically correct parts. Most tree species have female and male flowers on the same tree (monoecious). However, some species have different sexed trees (dioecious), such as boxelder, aspens, and willows. And then some species occur in strains of both!
Most tree flowers are not particularly showy, sometimes quite small, which may be why some folks are surprised to learn that all trees have flowers. On the other hand, cherries, magnolias, juneberries, redbuds, and dogwoods are among those trees that have exceptionally pretty displays.
Most of the showy flowers tend to be pollinated by insects, oftentimes bees. The more inconspicuous flowers tend to be pollinated by wind and rain. The latter strategy is more common among our north temperate tree species.
Hardwood fruits come in many forms and shapes, often peculiar to a particular family or genus. Nuts, or “hard mast”, are produced by oaks, beech, walnuts, and hickories. Note that the red oak group takes two years to produce an acorn. Birches and alders produce small cone-like structures, not to be confused with conifers. Maple helicopters are among the favorites for kids. But, ashes and elms also have “winged fruits”, with these wings called “samaras”.
Members of the legume family produce pods, such as black locust and honeylocust. The rose family sports a number of edible fruits, such as cherries, apples, and pears.
Then, about a half-dozen trees produce very tiny seeds with fluffy, cottony parts that float on the wind. “Cottonwood” gets its name from these sort of fruits, which can clog-up window screens in the spring and make messes for some homeowners. Heavy seed years can look like lightly drifted snow. Pussy willows are among this group, as well.
Our forest trees have a few odd fruits, too. Ironwood makes a hoppy-looking fruit, which is why it’s sometimes called “hop hornbeam”. Musclewood has a triangular, leafy fruit, with a nut-like seed at the base. Basswood produces small, hard, pea-like fruits. Hackberry features a blue berry-like fruit.
One of my favorites is the witch-hazel, which blooms in October, which is weird enough. The flowers have bright yellow stringy petals. The fuzzy fruits don’t grow until the next summer, and when ripe, forcibly eject the black seeds. This is fun to see, if you can be present at just the right popping time.
It should be no surprise that trees employ a wide variety of reproductive strategies for sexual reproduction. One should also remember that many tree species have asexual ways of reproducing such as sprouting, suckering, and layering. Layering is more of a subtropical and tropical strategy whereby a branch that comes in contact with the ground will grow roots. Our northern white-cedar is the best example of a temperate tree species that can layer. The ability of trees to sprout or sucker are often built into management system strategies.
Learning how trees reproduce is one more way to appreciate and enjoy forests. These diverse strategies are also integral to the forest management systems used in the Lake States, which are designed to encourage natural regeneration of forests. Why plant, when nature will do a better job for free?
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|Balsam fir cones from the top of a tree.||Witch-hazel flower in October.|
TRAILER- This website was created by a consortium of forestry groups to help streamline information about forestry and coordinate forestry activities designed to benefit the family forest owner and various publics that make up our Michigan citizenry. This website is maintained by Bill Cook, Retired Michigan State Extension Forester/Biologist. Direct comments to email@example.com or 906-786-1575.